(1) Field of the Invention
The present invention relates to a liquid catholyte aluminum-hydrogen peroxide seawater semi fuel cell which has particular utility as an energy source for underwater vehicles.
(2) Description of the Prior Art
Primary batteries employing aqueous electrolytes have been under development since the 1940s. U.S. Pat. Nos. 4,296,184 to Stachurski, U.S. Pat. No. 4,352,864 to Struthers, U.S. Pat. No. 4,485,154 to Remick et al, U.S. Pat. No. 4,492,741 to Struthers, and U.S. Pat. No. 5,496,659 to Zito show some of the electrochemical power cells that have been developed.
The '184 patent to Stachurski illustrates an electrochemical cell which has at least two compartments separated by a semi-permeable membrane. The compartments contain first and second solvents, electrolyte and electrode. The first compartment is divided by a membrane which behaves as a bipolar electrode during the passage of electric current.
The '864 patent to Struthers illustrates a fuel cell which has a metal anode immersed in a base electrolyte solution and connected with an electric circuit, a cathode comprising an acid solution, a carbon catalyst and electron distributor plate in that solution and connected with an electron supply and a wettable impermeable membrane and disposed between the electrolyte and cathode solution and establishing an acid-base reaction interface where hydroxide ions are generated for conduction through the electrolyte to the anode.
The '154 patent to Remick et al. illustrates an electrically rechargeable anionically active reduction-oxidation electric storage-supply system and process. The system and process use a sodium or potassium sulfide-polysulfide anolyte reaction and an iodide-polyiodide, chloride-chlorine, or bromide-bromine species catholyte reaction. The catholyte and anolyte are separated by an ion selective membrane permeable to positive sodium and potassium ions and substantially impermeable to negative bromide, chloride, iodide, sulfide and polysulfide ions.
The '741 patent to Struthers illustrates a primary fuel cell including an elongate case defining a central ion exchange compartment with opposite ends and containing a liquid ionolyte. The case also defines an anode section at one end of the case and including a gas compartment containing boron monoxide gas fuel, a liquid compartment between the gas compartment and the ion exchange compartment and containing a liquid anolyte. The ionolyte and anolyte are separated by a cationic membrane. The gas and liquid compartments are separated by an anode plate including an electron collector part, a catalyst material carried by the part and a gas permeable hydrophobic membrane between the boron monoxide gas and the catalyst material.
The '659 patent to Zito illustrates an electrochemical apparatus having at least one cell. Each cell has a positive electrode and a negative electrode with a dual membrane in each cell dividing it into positive chambers for posilyte and anolyte solutions which are recirculated through separate pumps and storage tanks and back to the chambers. The dual membranes in each cell provide a third chamber between the positive chamber and the negative chamber through which an idler electrolyte is circulated.
Emphasis has been placed on aluminum and magnesium anodes due to their high faradic capacity, low atomic weight and high standard potentials. Of particular interest is their application to undersea vehicles due to the availability of seawater to act as an electrolyte or electrolyte solution, thus further enhancing their effectiveness as an energy source on a systems basis.
A useful electrochemical energy source must permit high voltages, have a large storage capacity, operate safely, and reliably deliver the stored energy over extended discharge times. Therefore, the energy source must achieve a reasonably high cell potential, have a high Faradaic capacity, and have a high energy density at low current densities. Additionally, the energy source must be relatively inexpensive, environmentally, and SSN friendly, safe, capable of a long shelf life, and not prone to spontaneous chemical or electrochemical discharge.
High energy density Al-Aqueous primary batteries and semi-fuel cells for high current density (>500 mA/cm2) applications have been developed. These include aluminum-silver oxide and aluminum-hydrogen peroxide semi-fuel cells. U.S. Pat. No. 5,445,905 to Marsh et al. illustrates one such battery. In the Marsh et al. patent, a dual flow aluminum hydrogen peroxide battery is provided comprising an aqueous hydrogen peroxide catholyte, an aqueous anolyte, a porous solid electrocatalyst capable of reducing the hydrogen peroxide and separating the anolyte from the catholyte, and an aluminum anode positioned within the anolyte. The separation of the catholyte and anolyte chambers helps prevent hydrogen peroxide poisoning of the aluminum anode.
Despite these systems, there remains a need for a system with still better performance, particularly one in which the chemical reaction of the solution phase catholyte with the aluminum anode is eliminated.